Small containers are conventionally packaged into a shrink wrapped module by first placing a pre-cut sheet of shrinkable film (such as cross-linked polyethylene) into a cardboard tray then placing individual containers by hand into the tray in a prescribed pattern. The film is then manually draped over the top of the formed module and the module is transported, often with one or more intervening storage-handling steps, to a sealing operation in which an impulse heated wire device called an "L-Sealer" presses the top and bottom films together and seals them on two open sides of the module. The module is then turned around and the remaining open edge is similarly sealed.
The sealed package is then transferred through still another operation to an oven or heat tunnel to shrink the wrapping in two stages, the first stage shrinking the top of the wrapping and the second stage, after the package is withdrawn, inverted and the cardboard carton removed, shrinking the bottom of the wrapping.
In some operations, the collating of such containers into a shrink wrapable module has been mechanized by mass infeed conveyors delivering the articles to be packaged into a collection space defined by guide rails and stops, of predetermined size and configuration which, together in some cases with manual assist, results in the collection of the articles in a collated predetermined pattern.
In one such mechanized operation, the rear end of the package is formed by a reversible conveyor which removes articles collected in the predetermined pattern backwardly at a side or end of the collated article package to be wrapped. When the collated article module is then subsequently wrapped, the reversible conveyor is re-reversed and those collated articles at the front end form the front end of the subsequently formed package.
The transfer of such mechanized collated article collections into a shrinkable wrapped package has also been mechanized to some extent. In one such process, a vacuum lift mechanism raises the collated articles and then lowers them into a cardboard carton in which a pre-cut shrinkable film has been laid. When the articles are lowered into the carton a part of the shrinkable wrapping is laid over the top of the package and then transferred for subsequent sealing and shrinking, as in prior manual operations.
In another process, this has been accomplished by the collection of the collated articles on a platform capable, in conjunction with a hand held inverted tray, of capturing the collated articles on the top side, and inverting the collected articles. In this manner, the collated articles may be covered with a shrink wrapable film, which may in turn be covered by an inverted cardboard carton tray and the assembly in sandwiched style inverted so as thus to deposit the collated articles into a cardboard carton tray with a shrinkable film on the bottom side thereof between the collected articles and tray. The shrinkable film is then wrapped over the top of the inverted collected articles and transferred to other operations for sealing and shrinking.
In subsequently developed "automatic" collating and shrink wrapping machines, particularly referring to the "PLM" machine manufactured by Hirsch of Germany and the "Errani" and "Micron Errani" machines from Italy, groups of articles or bottles are automatically collated by pushing together successively formed rows of articles. Push members then propel the collated and collected group of articles or bottles through static guide rails (actually converging rails at one point in the "PLM" machine) and over dead plates. In the course of travel, the collated group of articles in each of these machines encounters an interposed, vertically draped sheet of shrinkable film, such as low density polyethylene, thereby wrapping the film about the front, bottom and top of the collated group of articles. An open-sided sleeve is then formed upon sealing the overwrapped film from top to bottom at the rear of the collated group of articles. In all of the known PLM, Errani and Micron Errani machines, this sleeve-wrapped grouping is then pushed over another dead plate onto a conveyor to still another sealing area at which the sides of the sleeve are sealed, either by resistive heat-sealing bars mating the top and bottom films at the sides of the package or by folding the top and bottom of the package on itself and continuing the package into the shrink wrapping position. In either case, the wrapped collated, collection of articles then is conveyed over still another dead plate into the heating space in which the wrapped film is shrunk.
In these prior art "automatic" machines, the collating mechanisms require intermittent sliding of groups of bottles, closure of guide rails over the collated package, and in general the movement of the collated package through static side rails or over dead plates, all to the detriment of the overall stability of individual articles, particularly in collected packages of small articles or containers.
Moreover, the rear and side sealing means in these machines require multiple stations and multiple transfers of the collated package while insufficiently retained in the collective grouping and over dead plates while insufficiently retained and into still another separate unit for the eventual shrinking of the shrinkable film.
Still further, in the "automatic" shrink wrapping machines available to date, the film supply and threading mechanisms and the tensioning means for the draped continuously supplied film are awkward and accessible only with some difficulty.
These and other similar factors having to do with the maintenance and set up of the machines result in inherent inefficiencies, complexities, bulk and expense in the manufacture and operation of prior art machines.
Keeping these problems in mind, it is a general objective of the present invention to provide a semi-automatic collating and shrink wrap packaging machine which is sufficiently small and simple to operate that it may be transported from line to line within a plant and operated by no more than one person. Moreover, it is within the general objective of the present invention to provide such a machine which is optimized with respect to movement of articles once collated so as to retain the collated group in a stable fixed pattern with minimum opportunity for upset of individual articles or disturbance of the pattern within the collated collection.
Still further, it is an object of this invention to provide such apparatus and specific subassemblies thereof in which the wrapped collated article grouping is effectively sealed and the wrapping shrunk in an essentially integral single unit with cycle time minimized and inter-position transfer mechanisms adapted to maintain the collated articles in their prearranged position until the final shrink wrapping is effected.
Another object is to provide convenient film supply, tensioning, rear sealing and cutting mechanisms in such apparatus.
Still another object of this invention is to provide such an apparatus which is conveniently adapted to handle different sized articles or containers and which, notwithstanding its general simplicity and ease of maintenance and operation, is especially adapted, with efficiency and reliability, to collate and shrink wrap in a sealed package small articles or containers which are generally unstable and difficult to maintain in a prearranged collated pattern.
These objects, and others which will become apparent in the course of the subsequent description of this invention, are all met by the invention, the description of which follows: